In an existing air-conditioning system including an air-conditioning apparatus and a ventilator, the ventilator performs the operation of replacing room air with outdoor fresh air, and a load is a cooling load (outdoor air load) in the case where an enthalpy of air introduced from outdoor air is high during cooling. Furthermore, as other heat loads, there are an indoor load generated in a room, and a frame load that enters through walls or the like of a building.
In order to handle a latent heat load of these heat loads, an evaporating temperature of refrigerant in an indoor heat exchanger of the air-conditioning apparatus is kept constant at a low temperature, and thus the latent heat load is handled.
However, there is a problem in that the operation in which the latent heat load is handled such that the evaporating temperature remains constant at a low temperature reduces operating efficiency. On the other hand, there is a problem in that an increase in the evaporating temperature enhances the operating efficiency, but results in an insufficient amount of handled latent heat, thereby increasing room air humidity and reducing comfort.
Thus, a latent heat-sensible heat separation-based air-conditioning system is provided (for example, Patent Literature 1). In the latent heat-sensible heat separation-based air-conditioning system, a ventilator that performs an outdoor air process and an air-conditioning apparatus are each independently controlled, an evaporating temperature in an indoor heat exchanger of the air-conditioning apparatus is controlled to be not less than a dew point temperature of room air so that a sensible heat load is mainly handled, and also, an evaporating temperature to secure an amount of dehumidification required for the ventilator that performs the outdoor air process is set so that a latent heat load is mainly handled.